Yesterday, Hurricane Irene weakened to become Tropical Storm Irene – but not before leaving at least 4 million homes without power and causing fuel shortages along the United State’s Atlantic coast. This hurricane brought on-land wind speeds of more than 85 mph in the continental United States, and maintained its hurricane status through most of its trek north. Though the storm had diminished by the time it hit New York today, it still carried 65 mph winds and drenching rain. And, with this wind came downed power lines and poles along the entire east coast, leaving many stranded without power.

The good news is that the east coast knew that this storm was coming. As David Biello said on Thursday – it’s best to be prepared. And, thanks to our nation’s storm tracking abilities, east coast utilities were able to ready road crews so they could repair power lines that were taken down by the high winds. Power plants lying within Irene’s projected path were able to prepare their facilities to be hit by the wind and rain, helping them to avoid extended supply disruptions.

But, even with this preparation, millions of American’s were faced with unplanned power outages – which is no surprise when you look at the size and complexity of the United States electric grid.

When the first power plants were built in the United States, they were located close to their customers – generally within a few miles. But, over time this distance has increased with growing populations, increasing electricity demand, and the electrification of rural America.

Today, there are more than 160,000 miles of transmission lines (the huge silver towers that you see along the road) and millions of miles of distribution lines running through the United States. While some of these lines run underground – especially in dense urban settings – the majority run overhead, supported by poles and towers. This web of wires moves electricity from the nation’s power plants to our homes and offices, supplying electricity whenever we demand it.

[Note: There is a great U.S. grid visualization tool available on NPR’s website]

Because of today’s connected grid, utilities are able to supply electricity to large areas with fewer power plants. Further, these connections make it easier for operators to balance supply and demand in the case of unexpected outages. But, this grid has also created a lot of expensive infrastructure that is susceptible to damage in extreme weather events.

In 2008, between $500 and $600 million was spent in region surrounding New Orleans, Louisiana after Hurricane Gustav damaged local electrical facilities. Four years earlier, Hurricane Ivan caused power outages from Venezuela to Canada – resulting in another huge price tag. It is reasonable to expect that, out of the $7 billion in estimated damages from Irene, a significant percentage of this total will be spent on bringing power back to the communities hit by the storm.

@geojellyroll – Good question. Thanks for asking it. To clarify – the specific plan proposed by @candide (solar or wind on homes) could have some environmental benefits. Using wind and solar – instead of the coal (with its air emissions, water use, and many other waste streams), natural gas (ditto) or nuclear (with its water use and dangerous solid waste stream) that make up the majority of our power generation fleet – could result in positive environmental gains by reducing emissions rates (pounds of greenhouse gases per kWh delivered) and water use rates (gallons per kWh delivered), etc. These rates could be further lowered by decreasing the distance between generation and use (local distributed generation), which could reduce or virtually eliminate transmission losses.